Two Mayo Clinic patients whose prostate cancer had been considered inoperable have no evidence of disease thanks in part to an experimental drug therapy that was used in combination with standardized hormone treatment and radiation therapy. The men were participating in an investigator sponsored clinical trial of ipilimumab. In these two cases, physicians say the approach initiated the death of a majority of cancer cells and caused extensive tumor shrinkage, allowing surgery. In both cases, the aggressive tumors had grown well beyond the prostate into the abdominal areas.

The patients first received a type of hormone therapy called androgen ablation, which removes testosterone and usually causes some initial reduction in tumor size. Researchers then introduced a single dose of ipilimumab, an antibody, which builds on the anti-tumor action of the hormone and causes a much larger immune response, resulting in massive death of the tumor cells. Both men experienced consistent drops in their prostate specific antigen (PSA) counts over the following weeks until both were deemed eligible for surgery. Then, during surgery, extensive tumor shrinkage was observed. One patient underwent radiation therapy after surgery; both have resumed their regular lives.

The research was supported by the Department of Defense, The Richard M. Schulze Family Foundation, the Mayo Clinic Cancer Center and the Mayo Clinic Center for Translational Science Activities. Medarex, Inc. provided the study drug free of charge and supported safety monitoring during the protocol.

Medarex Statement on Cautionary Factors

Except for the historical information presented herein, the statements relating to investigational antibody programs in this press release may constitute forward-looking statements, as defined in the Private Securities Litigation Reform Act of 1995, that are subject to certain risks and uncertainties that could cause actual results to differ materially from any future results, performance or achievements expressed or implied by such statements. Medarex disclaims, however, any intent or obligation to update these forward-looking statements. Risks and uncertainties include risks associated with product discovery and development of ipilimumab, as well as risks detailed from time to time in Medarex's public disclosure filings with the U.S. Securities and Exchange Commission (SEC), including its Annual Report on Form 10-K for the fiscal year ended December 31, 2008 and its quarterly reports on Form 10-Q. There can be no assurance that such development efforts will succeed or that developed products will receive required regulatory clearance or that, even if such regulatory clearance were received, such products would ultimately achieve commercial success. Copies of Medarex's public disclosure filings are available from its investor relations department.